This is an application for a new Program Project grant entitled, DNA Repair in Cancer Biology and Therapy. This is a laboratory-based, basic science program that features four inter-related projects that stress fundamental aspects of DNA repair, genome stability, cancer biology and tumor hypoxia, with a key long-term goal of developing novel anti-cancer therapies that target interconnected DNA repair pathways and/or exploit tumor hypoxia. Dr. Sartorelli will develop novel hypoxia-activated prodrugs that are designed to inhibit the repair factor, O6-alkylguanine-DNA alkyltransferase (AGT), as well as prodrugs that, upon activation in hypoxic cells, will damage and crosslink DNA. Dr. Glazer, the PI, will lead a project that focuses on the transcriptional regulation of the homology-dependent repair (HDR) genes, RAD51 and BRCA1, in hypoxic cancer cells. This project will probe how HDR is regulated in hypoxic cancer cells and will test the extent to which this regulation of HDR may render such cells vulnerable to agents that target interconnected repair pathways. Dr. Sweasy will study how repair factors in the base excision repair (BER) pathway vary in the normal population and in tumors. She will examine the phenotypes of BER variants in cells in culture and in mice using assays for mutagenesis, genetic instability, transformation, and tumor formation. She will examine how deficiencies in BER may play into the HDR pathway to guide the design of new cancer therapies. Dr. Sung will study how the HDR pathway is regulated at the level of protein-protein interactions, with a focus on the repair factors, BRCA2, FANCD2, and RAD51. One administrative and two scientific cores will provide essential services to the program. The Project leaders and Core directors are joined by common interests, a history of collaboration, and joint efforts in teaching and training that provide cohesiveness in support of this effort. The overall Program represents a significant commitment of the Yale University School of Medicine and the participating investigators to studies that have direct relevance to cancer biology and therapy.